There may also be more memory coping involved instead of just passing pointers around as well, but I'm not 100% sure. ---------------- Robert LeBlanc PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
On Mon, Jun 24, 2019 at 10:28 AM Jeff Layton <[email protected]> wrote: > On Mon, 2019-06-24 at 15:51 +0200, Hervé Ballans wrote: > > Hi everyone, > > > > We successfully use Ceph here for several years now, and since recently, > > CephFS. > > > > From the same CephFS server, I notice a big difference between a fuse > > mount and a kernel mount (10 times faster for kernel mount). It makes > > sense to me (an additional fuse library versus a direct access to a > > device...), but recently, one of our users asked me to explain him in > > more detail the reason for this big difference...Hum... > > > > I then realized that I didn't really know how to explain the reasons to > > him !! > > > > As well, does anyone have a more detailed explanation in a few words or > > know a good web resource on this subject (I guess it's not specific to > > Ceph but it's generic to all filesystems ?..) > > > > Thanks in advance, > > Hervé > > > > A lot of it is the context switching. > > Every time you make a system call (or other activity) that accesses a > FUSE mount, it has to dispatch that request to the fuse device, the > userland ceph-fuse daemon then has to wake up and do its thing (at least > once) and then send the result back down to the kernel which then wakes > up the original task so it can get the result. > > FUSE is a wonderful thing, but it's not really built for speed. > > -- > Jeff Layton <[email protected]> > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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